The invention relates to a method of manufacturing an item and an apparatus for manufacturing an item.
Known methods of manufacturing include injection moulding and die-casting. The manufacture of tooling for injection moulding or die-casting is a highly restrictive burden on industry, because of it""s high cost and lead times. Similar things are true of the cost of tooling for punch pressing, while the time taken by processes such as photo-chemical machining, electro and electroless plating and the environmental issues that surround these processes limit their use. The cost and the time taken to post-assemble products substantially reduces the flexibility and competitiveness of manufacturing industry.
So-called xe2x80x9cSolid Free Formxe2x80x9d (SFF) manufacture systems have been used in Rapid Prototyping (RP) applications starting in 1988 with 3D Systems""s introduction of their Stereolithography systems. The growth in the RP market has stimulated an accelerating rate of technological development in the field., and firms have developed different types of commercial systems for specific RP applications.
Solid Free Form (SFF) manufacture is essentially the computer controlled additive manufacture of three-dimensional physical forms. All of the commercial SFF systems employ the same basic principle. CAD data of the desired component is sliced into a number of horizontal layers. Each of these layers is built in turn on top of the preceding layer, by the precise addition of material, until the object has been completed. SFF manufacture also encompasses the computer-controlled manufacture of objects comprised of a single layer plus any other additive method of manufacture.
All of the commercial systems use direct computer control of their additive manufacturing processes. Consequently, the main advantages that these systems have over machining and moulding processes is that they can produce a one-off object with complex geometry far more flexibly and quickly than machining and moulding can. The main problem with all of these systems is that they cannot manufacture large batches of duplicate objects as fast as machining and moulding can. These systems have extremely limited capabilities for producing SFF objects with surface or internal colour, tone or doping. Furthermore, none of them can produce objects that are comprised of parts that are made of entirely different materials to the other parts.
Stereolithography RP systems work by using an UV laser to selectively expose the surface of liquid Ultra Violet (UV) reactive polymer to UV radiation (typically from a laser source). This causes the polymer to cure into a solid in the exposed area. The polymer that has been solidified is a physical realisation of a slice of a CAD model. The solidified material is supported on a platform. A new flat area of liquid UV reactive polymer is then laid over this layer by lowering of the platform into the liquid, and the exposure process is repeated to form another layer that bonds to the previous one. This process is repeated until the entire part has been completed.
Another UV polymer curing system is Cubital Ltd""s Solid Ground Curing (SGC) RP system. Here a thin layer of UV reactive polymer resin is spread over a platform and then exposed to UV radiation shone through a patterned mask. The transparent areas of the mask correspond to the required cross sections of a CAD model, and the UV radiation that passes through these areas cures part of the polymer layer into the pattern of the required cross section. Ionography technology is used to produce the masks that represent the required cross sections, and once a mask has been used it is erased and then re-imaged and inked with a new mask. A residual polymer cleaner removes the uncured polymer and then a spreader coats the cured polymer in wax. A cooling plate is used to accelerate the solidification of the wax, and once this has solidified it is milled flat by a milling head. The above processes are repeated until the entire model has been built. The wax is removed from the finished products by melting it away with hot (60xc2x0 C.) water.
By their nature all of the commercial polymer curing systems are limited to manufacturing objects out of UV reactive polymer. Consequently, the physical properties of these objects are not suitable for many functional applications.
Selective sintering systems have enabled objects to be made out of a wide range of powdered materials. As an example, one selective sintering method works by spreading a heat fusible powder on top of a moveable platform that can be lowered within a cylinder that defines the maximum part volume. The layer of powder is then selectively fused by a laser that defines the layer of the CAD model. The platform is lowered and a new layer of powder is deposited and subsequently selectively fused to the preceding layer. This process is repeated until the object is completed.
By combining materials and coating the powders with various binders, it is possible to make specialised powders, tailored to particular functional applications.
Another rapid prototyping technique is xe2x80x9claminated object manufacturexe2x80x9d (LOM). In this technique, objects are built by sticking sheets of material together. An uncut sheet is laid down and a heated roller is passed over it, which causes a coating of heat sensitive glue on the sheet to adhere it to the underlying sheet. A laser is then used to cut the sheet to the desired shape. Another layer is then added to the stack and the process is repeated. Most of the LOM RP systems are limited to manufacturing objects out of paper and polymers. Consequently, the physical properties of these objects are not suitable for many functional applications.
The xe2x80x9cFused Deposit Modellingxe2x80x9d (FDM) process uses low diameter thermo polymer wire-like filaments, which are extruded in a hot semi-molten form from a delivery head. The motion of the delivery head is computer-controlled. This allows the filament to be extruded in a pattern that depicts a layer of the required object and the object is built up in a layer-wise fashion out of the extruded layers that bond together when they cool. The cost of converting the thermo polymer to a filament can be extremely high and so objects that contain a large volume of the extruded filament can be extremely costly in comparison to injection moulded objects.
The use of hot melt jet printing technology in rapid prototyping is quite a new development. The principle is relatively straightforward. Solid ink is loaded into an ink reservoir and then heated so that the molten ink runs off and is channeled into a piezo-electric jet printer head. The printer then ejects the ink in molten droplet form onto a substrate upon which the droplets cool and thus solidify and adhere. Some systems, such as Sanders Prototyping""s Model Maker II use continuous-flow jet printers and others such as 3D Systems Actua 2100 use drop-on-demand (DOD) impulse jet printers. At present, these systems are limited to manufacturing objects out of waxes and thermo polymers. Consequently, the physical properties of these objects are not suitable for many functional applications.
MITs 3DP system and the Soligen Inc DSPC and Extrude Hone Corp.""s Prometal licensed versions use a different method from the previously mentioned selective sintering, but objects are still built by putting down a layer of powder. The difference is that the powder layers are bound together using a continuous jet printer to deposit a binder or solvent selectively onto the powder, and repeating the process consecutively until the required three dimensional object is constructed. Finally the object is removed from the loose powder and any unbound powder left on the object or trapped in inclusions is cleaned away.
Topographic Shell Fabrication (TSF) is a proprietary RP technology developed by Formus, USA. The TSF system is designed for manufacturing ultra large objects that can be the size of cars or even larger. The TSF system is comprised of a chamber, a layering device that deposits consecutive horizontal layers of silica powder into the chamber and a nozzle that selectively infiltrates a paraffin wax binder into the powder.
Objects of aspects of the invention are as follows:
The production of SFF objects out of a broad range of engineering and/or electronic materials.
A cost-effective SFF alternative to processes such as injection moulding, die casting, photo-chemical machining, electroless plating, electro plating, laminated circuit board manufacture or punch pressing.
An SFF system capable of competing with mass-production rates of processes such as injection moulding, die casting, photo-chemical machining, electroless plating, electro plating or punch pressing.
The direct SFF manufacture of SFF objects with a number of components, each made of different materials and/or more than one surface colour. This reduces or eliminates the post-assembly requirements currently associated with the manufacture of such objects.
An SFF system that is more environmentally friendly than processes such as injection moulding, die-casting, photo-chemical machining, electroless plating, electro plating or punch pressing.
The provision of and if required the subsequent removal of physical support for overhangs, large spans and disjointed volumes involved in a SFF object.
According to one aspect of the invention there is provided a method of manufacturing an item comprising the steps of:
controlling a printer means to print a layer of retaining material in a predetermined pattern onto a substrate;
applying a manufacturing material to be retained by the retaining material in substantially the predetermined pattern;
treating the manufacturing material so that it forms a continuous solid piece in substantially the predetermined shape of each distinct part of the pattern.
In this way, items can be manufactured rapidly and using equipment that is readily available and inexpensive.
According to another aspect of the invention there is provided apparatus for manufacturing an item including:
printer means for printing a layer of retaining material in a predetermined pattern on a substrate;
means for applying a manufacturing material to be retained by the retaining material in substantially the predetermined pattern; and,
means for treating the manufacturing material so that it forms a continuous solid piece in substantially the predetermined shape of each distinct part of the pattern.
The retaining material can take any suitable form. Thus, for example, it may comprise conventional printing ink, or may comprise water in a preferred embodiment. The retaining material may be arranged to be removed, suitably after or during treatment, for example, by evaporation. Alternatively, the retaining means may be arranged to be incorporated into the finished item, for example, by curing of an appropriate retaining means. In that case the retaining means may be coloured to result in colour in the manufactured item, for example on the surface of the item or internally. Similarly, different tones can be incorporated or other desirable characteristics such as doping can be achieved. Different retaining means may be used for different parts of the item to result in different colours or other characteristics. Indeed different retaining means may be used for the same part of an item so that for example colours can be mixed. Conveniently then the colours cyan, magenta, yellow, black and white may be used to enable the complete colour spectrum to be reproduced. The retaining material may be or have as a constituent a solvent, organometal, glue, decomposable material, curable material, or a low melting point material that can reduce the energy required to bond the powders involved in the method. In addition, if the retaining material contains glue or a low melting point material this may subsequently be used to aid the separation of solid material from the substrate. The retaining material may also be designed to allow catalytic reactions that promote or result in the solidification of the solid piece. In addition, the retaining material may also contain or be a parting agent.
The manufacturing material may be applied in any suitable form and may for example be applied as a liquid but preferably is applied as a powder. The powder may be applied in any suitable way such as:
by blowing the powder;
by electrostatically attracting or repelling the powder;
by electromagnetically attracting or repelling the powder;
by passing a substrate and its pattern through powder;
or by shaking powder onto the retaining material.
A coating roller may be rolled over the applied powder. This will promote even distribution, density and adherence of the powder. A number of different manufacturing materials may be applied in manufacture of the same item to result in different properties and/or colours. The manufacturing material may incorporate additional material to aid retention and/or to aid formation of the material into a continuous solid piece.
Excess manufacturing material is preferably removed before the step of treating the manufacturing material. The excess manufacturing material may be removed in any suitable way such as by blowing away the powder, by electrostatically attracting or repelling the powder, by electromagnetically attracting or repelling the powder, or shaking away the powder. Conveniently, the powder is removed by the accelerating the flow of a localised zone of atmosphere that is in close proximity to the powder. Preferably, the removed powder is recycled. The step of removal of excess powder will remove loose powder as well as removing any powder that is not well adhered to the retaining material.
If the manufacturing material needs to be supported, support material can be formed in a pattern that will give the required support. The support material may be of any type that may be easily removed from an item for example by mechanical, chemical, thermal or a combination or combinations of these means of removal. The material involved in the support must be capable of providing the required steadiness of hold for an item, and preferably, it should be solid at room temperature and in a powder form. The support material may be formed as follows:
by printing, applying and treating some substrates so that they have the support""s layers on them and others so that they have the item""s layers on them;
by printing, applying and treating a substrate so that a pattern of support is formed around a layer of an item that has previously been made but not deposited onto a platform or stack of layers;
by making the support out of the same material as the item and by using a pattern that produces fine structures of support that can be easily removed when the item is finished;
by depositing the support material where the support is required about a platform or stack of item layers;
by making the support out of the same material as the item and by printing, applying and treating so that a release agent is formed on the support. (This allows the support material to be easily removed when the item is finished);
by making the support out of the same material as the item and by printing release agent onto the support so that fine structures of support are formed that can be easily removed when the item is finished.
The support material may be applied after the excess manufacturing material has been removed.
The types of powders used are designed to act as the material for part, parts or all of an item, or the support for the item or combinations of these. Each type of powder can contain different particle sizes or distributions of particle sizes, and this can be used to enhance the properties of an item or support. Generally, the production processes for powders become more costly and wasteful as the particle sizes become smaller. Consequently, the use of different particle sizes can be used to reduce the cost of manufacture.
The manufacturing material may be treated in any appropriate way and may be treated by the application of energy for example in the form of heat, electrons, ionising radiation (for example, electrical, electromagnetic or ultrasonic radiation) or ultra violet radiation. In one preferred embodiment the manufacturing material is treated by means of shining a halogen lamp or lamps or one or more ceramic infrared emitters thereonto, and this may be used to turn the manufacturing material into a solid piece. Where heat is used, the method may then include controlling the heat and this may involve cooling the manufacturing material. This can increase the speed with which the next step can take place and can render the system more efficient. Means such as a roller mechanism may be used to compress and increase the density the treated manufacturing material.
Preferably, means is provided to adjustably control the height of the manufacturing material applied. The height control means may take any suitable form. Means to adjustably control the amount of manufacturing material applied may be provided and this may comprise the height control means. The control means may control the rate of application of manufacturing material, for example, by increasing or reducing the size of an aperture through which manufacturing material is applied, or by adjusting the vibration of the application device. In another embodiment and where the means for applying the manufacturing material moves relative to the substrate the control means may control how long the manufacturing material is applied for by controlling dwell time or speed of relative movement.
The substrate may be made of any suitable material such as paper, card, silicone or vulcanised rubber, cellophane or cellulose acetate, or may be made of metal such as stainless steel, nickel, nickel alloy, platinum, platinum alloy, tantalum, molybdenum, tungsten, titanium, vanadium, aluminium or aluminium alloy. Alternatively, the substrate may be made out of other strong engineering materials, for example composite materials. The substrate may be made of muscovite or phlogopite paper, woven or non-woven glass fibre, graphite composite or carbon fibre composite, kevlar (trade mark), glass, mica, or ceramic materials, such as alumina and alumina paper. Preferably, the substrate is made of a material that can be used again in the method, preferably without or with limited preparatory treatment before reuse. In another embodiment of the invention, the substrate is not reused and it can be dissolved, abraded, cut or burnt away or even peeled off or left in place. If the substrate is reused it is preferable that it is then returned to the printer means so that it can be used in the method as many times as it is required or is technically feasible to do so. In one embodiment, the solid material is used attached to the substrate but in a preferred embodiment, the solid material is separated from the substrate. In this case the substrate may then be made of or may include a coating of material to aid separation such as PVDF, PFA, PTFE, silicone, graphite, boron nitride or wax.
Not limiting the scope of the invention the substrates can be made in the form of cut sheets, web fed sheet, a continuous belt or a number of cylinders.
The method may be used for making thin items such as solder pre-forms, circuit boards, alternatives to die cut, punch pressed or pierced items, floor coverings, work surfaces or any other thin item that may have mechanical, electrical or optical applications or combinations of these applications. Consequently, the application of a single layer of manufacturing material may result in the final item. However, in many cases the method will further include the steps of aligning a plurality of the pieces of thus formed solid material and connecting the pieces together in a stack.
Each piece is aligned with the stack prior to it being applied to the stack, and a purely mechanically device can be used to ensure the alignment. This can involve using substrate or substrates that have edges, holes, lumps, recesses, pins, combinations of these or other mechanical registration aids that enable a purely mechanical device to align the substrates and pieces. In this instance, the printer may use the same or a similar device to control the alignment of its print, or the aids can be produced in register with the print. Even so, it is preferred that the alignment be controlled by a motor, sensor and controller arrangement. Preferably an indexing mark is applied to each substrate and the indexing mark is used in the alignment. In this instance, the sensor detects an indexing mark that has been made in alignment with the printed pattern on the substrate, and it then signals the controller motor unit to move the piece into alignment with the stack. The indexing mark may be applied after or preferably during the application of the manufacturing material. In another embodiment of the invention, the sensor detects an indexing mark that was used to register the printing of the pattern, and it then signals the controller motor unit to move the piece into alignment with the stack. Alternatively, a sensor, controller, motor unit can register a platform with piece prior to connecting the piece with a platform or a stack. Furthermore, the method may also involve organising the substrates and their pieces so that they are subsequently deposited in correct order in relation to one another. At the point of connecting the pieces together in a stack, stack height control is performed, and this can be achieved for example by the use of stacks of micrometers, shims or a Z motion control device.
The retaining means is preferably applied to only one of the surfaces of the substrate, preferably the top surface of the substrate. The substrate may then be moved, for example, inverted, so that the solid material is aligned. The substrate can then be moved so that the solid material is deposited, for example, downwards, on a platform or on stack of solid material layers so causing the deposited solid material to form another layer on the stack. The deposition can be done in such a way that the solid material forms the main contact with the platform or stack in comparison to the contact of the retaining means if there is any at all. The deposition can be continued in this way until the required item is manufactured. In fact, in this case the item is composed of a plurality of item layers in a stack.
Duplicate layers may be consecutively constructed from common printing means. There are particular advantages in doing this in that the same pattern can be applied as many times as the number of identical layers being manufactured. Changing the pattern to be printed takes time and processing power, whereas repeating a pattern can be done rapidly. This increases the speed of manufacture because the changing of patterns is likely to be a major factor that may slow the speed. It is thus much quicker to make duplicate layers consecutively in this way than it is to change to produce a new pattern for each duplicate layer. The means for applying manufacturing material may be specific to the printer means, or common to a number of printer means and preferably further the means for treating the manufacturing material may be specific to the applying means or common to a number of applying means. In addition, the patterns for duplicate and dissimilar layers may be concurrently printed from a number of printing means, and this may be used to increase the speed at which items can be manufactured.
Several items may be constructed concurrently from common printing means. This increases the speed of manufacture as the printing is likely to be the fastest step of the method and it renders the system more efficient. Changing the pattern to be printed takes time and processing power, whereas repeating a pattern can be done rapidly. It is thus much quicker to make two items concurrently in this way than to make them one after the other using the same apparatus. Preferably, the means for applying manufacturing material is also common and preferably further the means for treating the manufacturing material is also common.
The pieces of solid material in layers may be connected in any suitable way as appropriate to the manufacturing material used and/or the retaining material where that is incorporated at the contact surface. Thus, the pieces of solid material in layers may be connected by the controlled application of pressure and/or ultrasonic energy, heat, ultraviolet radiation, ionising radiation, organometal, glue, solvent or combinations of these. In another embodiment of the invention, a cooling device is used to cool and thus stabilise each layer after or during its deposition onto the stack or platform.
Where the substrate is removed from the manufacturing material it may be removed at the stage when the solid material thereon has been placed on or connected together on a stack.
The method may be conducted in a controlled atmosphere that may be neutral or may be arranged to cause beneficial interactions.
A computer may control the pattern that a printer means prints. It is preferable that this control is by means of the conversion of data from a CAD data via a slicing algorithm into an image form such as bitmap form.
The printer means can be a printer of any suitable type and preferably comprises a jet printer and may or alternatively comprise a computer to plate printer, direct imaging printer or a screen printer. The jet printer may for example be a continuous flow jet printer, a thermal jet printer, an impulse jet printer, a valve jet printer or a spray jet printer.
Not limiting the scope of the invention, the support material may be a polymer such as phenolic, epoxy, polyethylene oxide, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, poly (2-ethyl-2-oxazoline) or nylon. Sugar such as maltose, fructose or glucose can also be used as a support and salts such as magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, sodium oxide or sodium hydroxide, sodium chloride can be used as an alternative. Ceramic materials such as alumina, zirconium silicate, molochite, china clay or silica may be used, and metals such as zinc or tin may be used. Wax, resin, gelatin, talc, starch or gum arabic may also be used a support material. A combination of a number of the previously mentioned materials may be used. The support material may also be a material that is soluble in water or organic solvent
Not limiting the scope of the invention, the manufacturing material can be a polymer such as nylon, polycarbonate, polystyrene, phenolics, polyethylene, ABS or epoxies. Metals such as zinc, tin, solders, copper, stainless steels, steel, tungsten carbide/cobalt, bronze or aluminium may also be used for manufacturing material. Powders that are or are based on ceramic materials such as silica, zirconium silicate, molochite, china clay, alumina may also be used. The material may also be comprised of or incorporate a glass. The material may also be a combination of a number of the previously mentioned materials.
An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:
FIG. 1 is a perspective view of the apparatus of the embodiment of the invention;
FIG. 2a is a perspective view of an item and support material made by the apparatus of FIG. 2b is the view of FIG. 2a with the support material removed;
FIG. 3 is a detail view of the structure of part of the item; and,
FIG. 4 is a detail view of the structure of part of an item constructed from a different powder.